Like my name doesn't have my answer
Php is growing to more then 50% of all ssi's and is alot more effective with allot less work (just my opinion), but ASP has Microsoft to back it with effective tools like visual studios and with asp, you can work wish access, and has multiple language suport, like vb and jscript.
I'd suggest learning a little or both, like writing the date or getting form data, then see which structure you like the best. Their both good languages, but it's all about preferences, like choosing between IE and FF.
Good luck and have fun *cough*php*cough*
